1. Field of the Invention
Exemplary embodiments of the invention pertain to the art of turbomachine combustion systems and, more particularly, to a flame suppression system for protecting a multi-tube nozzle.
2. Description of the Related Art
In general, gas turbine engines combust a fuel/air mixture that releases heat energy to form a high temperature gas stream. The high temperature gas stream is channeled to a turbine via a hot gas path. The turbine converts thermal energy from the high temperature gas stream to mechanical energy that rotates a turbine shaft. The shaft may be used in a variety of applications, such as for providing power to a pump or an electrical generator.
In a gas turbine, engine efficiency increases as combustion gas stream temperatures increase. Unfortunately, higher gas stream temperatures produce higher levels of nitrogen oxides (NOx), an emission that is subject to both federal and state regulation. Therefore, there exists a careful balancing act between operating gas turbines in an efficient range, while also ensuring that the output of NOx remains below mandated levels.
Low NOx levels can be achieved by ensuring very good mixing of the fuel and air and burning a lean mixture. Various techniques, such as Dry-Low NOx (DLN) combustors including lean premixed combustors and lean direct injection combustors, are used to ensure proper mixing. In turbines that employ lean pre-mixed combustors, fuel is pre-mixed with air in a pre-mixing apparatus prior to being admitted to a reaction or combustion zone. Pre-mixing reduces peak combustion temperatures and, as a consequence, also reduces NOx output. However, depending on the particular fuel employed, pre-mixing may cause auto-ignition, flashback and/or flame holding within the pre-mixing apparatus. As one might imagine, cases of auto-ignition, flashback and/or flame holding within the pre-mixing apparatus can be damaging to machine components. At a minimum, such conditions can affect emissions as well as performance of the combustion system, and may result in degradation or destruction of equipment.
Thus, what are needed are methods and apparatus for addressing problems associated with auto-ignition, flashback and/or flame holding within the pre-mixing apparatus.